Cryptographic key generation using multiple random sources

PRIORITY CLAIM

The present application is a National Phase entry of PCT Application No. PCT/EP2019/061237, filed May 2, 2019, which claims priority from EP Patent Application No. 18174203.2, filed May 24, 2018, each of which is hereby fully incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to improvements to the generation of cryptographic keys.

BACKGROUND

Hardware Security Modules (HSMs) are network-connected physical devices tasked with the secure generation, storage and provision of cryptographic keys for use by consuming resources such as computer systems, appliances, devices, software and users. For example, HSMs generate, store and provide public/private key pairs. HSMs employ deterministic random number generators to generate pseudo-random numbers for cryptographic key generation. An increasing use of technologies such as internet-of-things communications, distributed data structures for trusted storage of data and transactions (e.g. blockchains) and intercommunicating virtualized computer systems requires the generation of increasingly large volumes of cryptographic keys. The challenge is especially acute in view of the sheer volume of single use keys being requested of HSMs and being used and disposed over relatively short periods.

The use of pseudo-random numbers as a basis for key generation is widely acknowledged to be vulnerable due to their deterministic nature. Thus, the key generation facilities of such HSMs are not suitable for high-volume key generation. HSMs are also subject to strict compliance requirements. These compliance requirements can include, for example: the Common Criteria for Information Technology Security Evaluation (abbreviated as Common Criteria or CC) (international standard ISO/IEC <b>15408</b>) for computer security certification; and Federal Information Processing Standard (FIPS) Publication 140-2, (FIPS PUB 140-2), a U.S. government computer security standard used to approve cryptographic modules. The need for such compliance leads to constraints on HSM capabilities such as rates of undertaking cryptography operations including key generation. Furthermore, the very nature of HSMs as secure and compliant components protected from interference and tampering renders them unsuitable or impossible for modification such as upgrading to increase processor, memory or other resources.

Thus, there is a challenge in providing requisite cryptographic operations to satisfy the growing demands of modern technology while retaining the necessary security compliance provided by HSMs.

SUMMARY

The present disclosure accordingly provides, in a first aspect, a computer implemented method of generating cryptographic keys for a hardware security module (HSM), the method comprising: generating a plurality of cryptographic keys and storing the cryptographic keys for use by the HSM in providing cryptography functions, wherein the cryptographic keys are generated based on numerical data generated by a hardware random number generator, such that a rate of generation of the cryptographic keys unconstrained by the resources of the HSM, wherein the hardware random number generator operates based on a plurality of statistically random entropy data sources originating from natural phenomena so as to increase a degree of randomness of the numerical data.

In some embodiments the generated cryptographic keys are stored in the HSM by invoking a storage function of the HSM.

In some embodiments storage of the cryptographic keys in the HSM is scheduled to occur at times when the HSM is operating in a low utilization state relative to an average utilization state of the HSM.

In some embodiments the natural phenomena include one or more of: one or more statistically random noise signals; and quantum phenomena such as photoelectric effects.

The present disclosure accordingly provides, in a second aspect, a computer system including a processor and memory storing computer program code for performing the method set out above.

The present disclosure accordingly provides, in a third aspect, a computer program element comprising computer program code to, when loaded into a computer system and executed thereon, cause the computer to perform the method set out above.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram a computer system suitable for the operation of embodiments of the present disclosure.

<figref idref="DRAWINGS">FIG. 2</figref> is a component diagram of a computer implemented method of generating cryptographic keys for an HSM in accordance with an embodiment of the present disclosure.

<figref idref="DRAWINGS">FIG. 3</figref> is a flowchart of a computer implemented method of generating cryptographic keys for an HSM in accordance with an embodiment of the present disclosure.

<figref idref="DRAWINGS">FIG. 4</figref> is a component diagram of a computer implemented method of generating cryptographic keys for a plurality of HSMs in accordance with an embodiment of the present disclosure.

<figref idref="DRAWINGS">FIG. 5</figref> is a flowchart of a computer implemented method of generating cryptographic keys for a plurality of HSMs in accordance with an embodiment of the present disclosure.

<figref idref="DRAWINGS">FIG. 6</figref> is a component diagram of a computer implemented method of generating cryptographic keys for an HSM in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram of a computer system suitable for the operation of embodiments of the present disclosure. A central processor unit (CPU) <b>102</b> is communicatively connected to a storage <b>104</b> and an input/output (I/O) interface <b>106</b> via a data bus <b>108</b>. The storage <b>104</b> can be any read/write storage device such as a random-access memory (RAM) or a non-volatile storage device. An example of a non-volatile storage device includes a disk or tape storage device. The I/O interface <b>106</b> is an interface to devices for the input or output of data, or for both input and output of data. Examples of I/O devices connectable to I/O interface <b>106</b> include a keyboard, a mouse, a display (such as a monitor) and a network connection.

<figref idref="DRAWINGS">FIG. 2</figref> is a component diagram of a computer implemented method of generating cryptographic keys for an HSM <b>206</b> in accordance with an embodiment of the present disclosure. The HSM <b>206</b> is provided as a physical or virtualized compliant security module for providing cryptography functions for computing, networking, communications, data storage and other applications as will be apparent to those skilled in the art. The HSM <b>206</b> can include functions suitable for triggering the generation, storage and use of cryptographic keys. According to embodiments of the present invention, the HSM <b>206</b> is at least partly, and in some embodiments wholly, relieved of the task of cryptographic key generation in order that such generation can be performed in a manner that is unconstrained by the resources of the HSM <b>206</b> and that does not suffer the considerable disadvantages of key generation based on deterministic random number generation.

Cryptographic keys are generated by a key generator <b>204</b> as a secure hardware, software, firmware or combination component. The key generator <b>204</b> is provided with computing resources sufficient for the generation of large quantities of cryptographic keys and, in particular, for the generation of quantities of cryptographic keys exceeding at a rate exceeding the generation of keys by the HSM <b>206</b>.

The key generator <b>204</b> operates on the basis of random numbers generated by a hardware random number generator <b>202</b> which generates random numbers based on statistically random entropy data <b>200</b>. Hardware random number generators can be known in the art as “Truly random number generators” (TRNG), the word “truly” being accepted by those skilled in the art but being better described as a hardware random number generator. The hardware random number generator <b>202</b> provides random numbers on the basis of the statistically random entropy data <b>200</b> which can include, for example, physical phenomena such as statistically random “noise” signals such as thermal noise, photoelectrical noise, beam splitting and/or other quantum phenomena.

Thus, in use, cryptographic key generation takes place away from the HSM <b>206</b> based on a hardware random number generator <b>202</b>. Accordingly, the determinism of the random numbers used as a basis for key generation is considerably reduced and security of generated keys considerably enhanced. Furthermore, the key generator <b>204</b> is unconstrained by the resources of the HSM <b>206</b> so permitting the generation of keys in volumes exceeding that possible by the HSM <b>206</b>.

Keys generated by the key generator <b>204</b> are stored for use by the HSM <b>206</b>. In some embodiments, the keys are stored in the HSM <b>206</b> by a storage function of the HSM <b>206</b>, key storage being a typical core function of a HSM. In use, the HSM <b>206</b> can be populated with generated keys by the key generator <b>204</b> such that the HSM <b>206</b> can utilize keys as required by consuming entities operating with the HSM <b>206</b>. Since the performance of the HSM <b>206</b> is constrained, it is beneficial if the process of triggering storage operations for keys in the HSM <b>206</b> is scheduled to occur at times when the HSM <b>206</b> is operating in a low utilization state. For example, when demands on the HSM <b>206</b> are relatively lower than an average utilization state of the HSM <b>206</b>, the key generator <b>204</b> can populate a storage for keys in the HSM <b>206</b> for subsequent use by the HSM <b>206</b>. Additionally, or alternatively, key population of the HSM <b>206</b> can be triggered by a rate, extent or level of consumption of keys by the HSM <b>206</b> such that, for example, when a number of available keys in the HSM <b>206</b> falls below a threshold number or proportion, or when a rate of consumption meets a threshold rate, the key generator <b>204</b> can operate to populate the HSM <b>206</b> with further keys.

<figref idref="DRAWINGS">FIG. 3</figref> is a flowchart of a computer implemented method of generating cryptographic keys for an HSM <b>206</b> in accordance with an embodiment of the present disclosure. Initially, at <b>302</b>, the method generates a plurality of cryptographic keys for use by the HSM <b>206</b> in providing cryptography functions. The keys are generated based on numerical data generated by the hardware random number generator <b>202</b>. At <b>304</b> the cryptographic keys are stored for use by the HSM <b>206</b>.

<figref idref="DRAWINGS">FIG. 4</figref> is a component diagram of a computer implemented method of generating cryptographic keys for a plurality of HSMs <b>406</b> in accordance with an embodiment of the present disclosure. Many of the elements of <figref idref="DRAWINGS">FIG. 4</figref> are identical to those described above with respect to <figref idref="DRAWINGS">FIG. 2</figref> and these will not be repeated here. The arrangement of <figref idref="DRAWINGS">FIG. 4</figref> differs in that a plurality of HSMs <b>406</b> are provided for the consumption of keys generated by the key generator <b>404</b>. To accommodate the consumption of keys by multiple HSMs <b>406</b> and to ensure key availability in sufficient volumes to satisfy the potentially collectively high demand for keys by the HSMs <b>406</b>, the key generator <b>404</b> stores generated keys in a secure key store <b>405</b> external to the HSMs <b>406</b>. In this way, a rate of key storage by the key generator <b>404</b> is not hindered by any particular or generalized performance constraint resulting from the available resources of one or more of the HSMs <b>406</b>. Thus, the key generator <b>404</b> generates keys in volume and securely stores the keys in the key store <b>405</b>. Subsequently, requirements for keys arising in an HSM <b>406</b> can be satisfied by populating such HSM with already generated keys stored in the key store <b>405</b>. The provision of keys to a HSM in the set of HSMs <b>406</b> can be undertaken by the key generator <b>404</b> or a separate secure component (not illustrated). For example, the key generator <b>404</b> can recognize or respond to a requirement for keys by a HSM and satisfy the requirement by providing keys to the HSM from the key store <b>405</b>. The keys can be stored in such a HSM by, for example, a key storage function of the HSM.

To permit efficient management of the keys in the key store <b>405</b> and recognize keys that are utilized by an HSM, keys that are provided to a HSM for use are flagged as utilized in the key store <b>405</b>. In this way, flagged keys can be identified to prevent multiple HSMs utilizing the same key.

<figref idref="DRAWINGS">FIG. 5</figref> is a flowchart of a computer implemented method of generating cryptographic keys for a plurality of HSMs in accordance with an embodiment of the present disclosure. Initially, at <b>502</b>, the method generates a plurality of cryptographic keys for use by a plurality of HSMs <b>406</b>. The keys are generated based on numerical data generated by the hardware random number generator <b>402</b>. At <b>504</b> the cryptographic keys are securely stored in a key store <b>405</b> for use by the HSMs <b>406</b>. At <b>506</b> the method determines if a key is utilized by a HSM and, where a key is utilized, the key is flagged as utilized at <b>508</b>.

<figref idref="DRAWINGS">FIG. 6</figref> is a component diagram of a computer implemented method of generating cryptographic keys for an HSM <b>606</b> in accordance with an embodiment of the present disclosure. Many of the features of <figref idref="DRAWINGS">FIG. 6</figref> are identical to those described above with respect to <figref idref="DRAWINGS">FIG. 2</figref> and these will not be repeated here. <figref idref="DRAWINGS">FIG. 6</figref> further includes a plurality of statistically random entropy data sources <b>600</b>, such as the data sources previously described with respect to <figref idref="DRAWINGS">FIG. 2</figref>. Thus, in embodiments according to the arrangement of <figref idref="DRAWINGS">FIG. 6</figref> the hardware random number generator <b>602</b> operates based on the plurality of data sources <b>600</b> so as to increase a degree of randomness of the numerical data on which basis the key generator <b>604</b> generates keys.

In one embodiment, the selection or number of data sources is informed by a consuming HSM <b>606</b> so as to increase the non-deterministic nature of the random number generation utilized for key generation.

Insofar as embodiments of the disclosure described are implementable, at least in part, using a software-controlled programmable processing device, such as a microprocessor, digital signal processor or other processing device, data processing apparatus or system, it will be appreciated that a computer program for configuring a programmable device, apparatus or system to implement the foregoing described methods is envisaged as an aspect of the present invention. The computer program may be embodied as source code or undergo compilation for implementation on a processing device, apparatus or system or may be embodied as object code, for example.

Suitably, the computer program is stored on a carrier medium in machine or device readable form, for example in solid-state memory, magnetic memory such as disk or tape, optically or magneto-optically readable memory such as compact disk or digital versatile disk etc., and the processing device utilizes the program or a part thereof to configure it for operation. The computer program may be supplied from a remote source embodied in a communications medium such as an electronic signal, radio frequency carrier wave or optical carrier wave. Such carrier media are also envisaged as aspects of the present invention.

It will be understood by those skilled in the art that, although the present disclosure has been described in relation to the above described example embodiments, the invention is not limited thereto and that there are many possible variations and modifications which fall within the scope of the invention.

The scope of the present disclosure includes any novel features or combination of features disclosed herein. The applicant hereby gives notice that new claims may be formulated to such features or combination of features during prosecution of this application or of any such further applications derived therefrom. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in the specific combinations enumerated in the claims.